Officials are probing how a 51-year-old highway bridge came to collapse in the Italian port city of Genoa yesterday, killing at least 26 people and injuring 16 others as it sent dozens of vehicles tumbling into a heap of concrete and twisted steel.

NSW CSG operation under investigation

Possible leaks of toxic water stemming from a coal seam gas operation in a northern NSW forest are being investigated by the state's environmental watchdog, conservationists say.

When the lining of waste water storage ponds in the Pilliga forest were breached a groundwater aquifer was "contaminated" with uranium 20 times higher than safe drinking water guidelines, Lock the Gate's Carmel Flint said.

"Requests by the Lock the Gate Alliance under freedom of information have confirmed the Environmental Protection Agency (EPA) is investigating two waste water storage dams at Tintsfield, southwest of Narrabri," the prominent anti-CSG group said.

Elevated levels of salinity and naturally occurring heavy metals have also been detected.

"Santos has already been fined for contaminating groundwater with uranium and other heavy metals at its CSG waste water ponds in the Pilliga Forest and now we learn that two more holding ponds are under investigation for similar leaks" Ms Flint said.